a. Field of the Invention
The present invention relates to digital signal processing and, more particularly, to the manipulation and/or conversion of MPEG-2 compressed data.
b. Description of the Prior Art
In the world of television production studios, there is a myriad of equipment necessary to eventually broadcast or transmit a television signal. The production studio has many video feeds (inputs) at its disposal for selection of the video signal to be used. Examples of video feeds are live feeds, network feeds, satellite feeds, and locally generated video content. Likewise, the production studio has many video destinations (outputs) that may be selected in routing the video signal. Examples of such video destinations are tape machines for archival purposes, production switchers for special effects, and the broadcast antenna.
The video feeds generally utilize the SMPTE (the Society of Motion Picture and Television Engineers) 259 (M) standard. This standard describes a serial digital interface for system M (525/60) digital television equipment operating with either 4:2:2 component signals or 4f.sub.sc NTSC (National Television Standards Committee) composite digital signals. The output equipment also utilizes the standard.
In order to manage the various inputs and outputs, studios generally utilize a device known as a video router. A typical video router takes the video input streams or signals in SMPTE-259 compatible format and routes the signals to the desired destination. In order to switch from one video feed to another video feed, the video router performs the change or switch in video feed during the vertical blanking interval and, being NTSC, the frame rates of all the video through the router should be 29.97 Hz. The typical video router as described above is a rather complex and costly piece of equipment due to the electronics needed to perform the transfer or router functions.
While the SMPTE-259 standard is a digital standard, in order for studios to start producing, processing and transmitting high definition television (HDTV), it will be necessary to have MPEG-2 compatible video input and output devices such as HDTV cameras, HDTV monitors, and HDTV post production equipment to name a few. Thus, when studios start producing, processing and transmitting high definition television (HDTV) material, the SMPTE-259 router will no longer function. Replacing the SMPTE-259 router will most likely be one of the most expensive pieces of equipment.
It is thus an object of the present invention to provide a method and apparatus for converting different types of input bitstreams into an SMPTE-259 compatible bitstream, particularly for use by an SMPTE-259 router.
It is more specifically one object of the present invention to provide a method and apparatus for converting an MPEG-2 bitstream into an SMPTE-259 compliant format to allow the MPEG-2 compressed HDTV bitstream to be routable via an SMPTE-259 router.
It is another object of the present invention to provide a means whereby a television studio can route both the standard definition (e.g. NTSC) video signals and the HDTV video signals over the same video router.
It is still another object of the present invention to provide a "frame dropper" method and apparatus to minimize the loss of information between the frame rates of the input and output bitstreams for the conversion of one bitstream format into another bitstream format.
It is yet another object of the present invention to provide a word translator that converts characters that are forbidden in the SMPTE-259 standard but could exist in the bitstream as "escape characters."